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Seven houses condemned as major Florida sinkhole expands

Florida state especially prone to sinkholes because of its construction atop limestone

Tue, Aug 8, 2017, 15:42Updated: Tue, Aug 8, 2017, 15:45

A sinkhole (above) at Land O’Lakes, Florida has expanded and now stretches 260ft (80m) at its widest point, the Tampa Bay Times reported. Photograph: Luis Santana/Tampa Bay Times/AP

Seven houses have now been condemned in Land O’Lakes, Florida, thanks to the county’s largest sinkhole in 30 years.

Two homes were destroyed when the ground gave way on July 14th, but the sinkhole has since expanded and now stretches 260ft (80m) at its widest point, the Tampa Bay Times reported. Two more houses along its edge were condemned on Saturday, followed by three on Sunday, according to a Pasco County news release.

Ceres Environmental Services has been contracted to remove debris from the sinkhole, and five container-truckloads were carted off Saturday, according to the news release.

When rainwater seeps into the ground, the acids it contains gradually erode particular types of bedrock - limestone or sandstone for example

On Monday, another contractor began removing contaminated water. The full clean-up is expected to take months, the county said.

Sinkholes are the culmination of a process that can occur over centuries or even millenniums. When rainwater seeps into the ground, the acids it contains gradually erode particular types of bedrock - limestone or sandstone for example. Natural cracks and cavities in the bedrock slowly expand, and the soil above it begins to fall through.

Sediment in cracks

At first, the upper layers can still bear the weight of the buildings above them. But eventually, as the sediment slips through the cracks like sand through an hourglass, the ground gives way. Heavy rainfall can contribute to a sudden collapse.

Florida is especially prone to sinkholes, more so than any other state, because it sits on limestone. The composition of the sediment above the bedrock is also a factor, making some parts of the state more unstable than others.

Central Florida, including the Orlando and Tampa areas, is at the greatest risk; parts of Northern Florida are also particularly vulnerable. Land O’Lakes is about 30km north of Tampa in a region of the state known as Sinkhole Alley.

Fatalities from sinkholes are very rare. In 2013 one swallowed up a man, Jeffrey Bush, as he lay in bed in Seffner, Florida, east of Tampa. His body was never recovered.